Amphibious vehicle steering

ABSTRACT

An amphibious vehicle has retractable wheels ( 2, 3 ) attached to hubs ( 2 ), and a planing hull ( 10, 11, 3 ). Front wheels are arranged to be steered by a power assisted transversely mounted element ( 16 ), which may be a rack and pinion unit. The element may be linked to the wheels by links ( 14, 14′ ), which fold up to position ( 14″ ) when the wheels are retracted. Actuating rod ( 28 ) is mounted to said element, and arranged for transverse movement. A flexible coupling means, such as cable ( 34 ) and sleeve ( 36 ), connects rod ( 28 ) to a steerable part ( 42, 4 ) of a marine propulsion unit, to effect marine steering. Road and marine steering may be operable simultaneously. More than one front steered axle, and/or marine propulsion unit, may be fitted. The steering system is readily adapted to all kinds of power assisted steering, and also to “steer by wire”.

Amphibious vehicles, hereafter “amphibians”, are frequently steered intheir land and marine modes by the same steering wheel. A simple form ofamphibian steering is shown in U.S. Pat. No. 5,727,494 (Caserta). InCaserta's proposal, a steering cable is arranged between a rearpropulsion unit and the inner shaft of the steering column, which thecable is wound around, and thence back to the marine propulsion unit.Whilst this is a simple arrangement, it is unsuitable for high speedplaning amphibians, where the force required to steer the propulsionunit is high. That is, the mechanical advantage of the Casertaarrangement is low. Where an automotive steering column is used, thereis a high risk that the steering cable according to Caserta willconflict either with the mechanism designed to ensure crushability ofthe steering column in an accident; or alternatively, with anytelescopic adjustment mechanism designed to ensure an ergonomic drivingposition.

In another proposal shown in U.S. Pat. No., 5,590,617 (Gore), thelinkages between the rear marine propulsion unit and the steeringarrangement at the front of the vehicle are bulky and heavy, at alocation at the front of the vehicle where weight has to be carefullycontrolled in a planing amphibian. Furthermore, the steering accordingto Gore is conformed so as to be operable in either a road mode or amarine mode. To allow this duality, the road steering system depends foroperation on the steering rack being held in place by pressurizedpneumatic rams. This is somewhat alarming from a safety viewpoint.

It is considered advantageous to have road and marine steering systemwhich can be operated simultaneously. This simplifies control systems,as there are less changes to be made in converting from road mode tomarine mode or vice versa. Also, when manoeuvring at low speed in water,particularly to direct an amphibian to a slipway, the steering effect ofdependent road wheels may be at least as great as that of, for example,a steering nozzle attached to a jet drive. Furthermore, if both systemscan be operated together, there is no need for complex systems to ensurethat when one or the other system is switched in, it is always initiallycentred. Finally, there is a safety advantage, in that in the unlikelyevent of breakage or seizure of the steering cable, a second steeringsystem is available. In this context, it should be noted that the marinesteering is self-centring. In the absence of any control input orrestraint of movement, passage of water through the jet nozzle will tendto centre the nozzle.

It is an object of the invention to provide a steering system for a planamphibian in which the steering system is balanced, so that powerassistance to the road steering matches the power assistance required toovercome the self centring tendency of the marine propulsion unitrunning at high speed. Another object is to reduce the bulk of parts ofthe steering assembly in the region between the front wheels, which haveto retract to reduce water resistance in a planing amphibious vehicle.

According to the invention, there is provided an amphibious vehiclehaving retractable wheels and a planing hull, a marine propulsion unit,front wheels arranged to be steered by means of a power assistedtransversely mounted element, an actuating rod mounted to said element,the rod arranged for transverse movement, and a flexible coupling meansconnecting said actuating rod to a steerable part of the marinepropulsion unit, so that transverse movement of said element steers thepart of the marine propulsion unit.

Preferably, the element is linked by means of a link to each wheel, thelinks being arranged to fold upwards on retracting the wheels. Both roadand marine steering may be arranged to be operated simultaneously. Thetransversely mounted element may be a rack and pinion steering system.The flexible coupling means is preferably a push-pull cable and abell-crack means attached to the actuating rod. The actuating rod may bemounted in front of a steering column. The push-pull cable arrangement,comprising a cable slidable in a sleeve, is readily arranged so as tofit between body members and the vehicle power train with a minimumbending radius of 150 mm. In one embodiment, the cable is between 12 and13 mm in diameter, whilst the outer sleeve of the cable is between 15and 17 mm in diameter.

The steering system may be readily adapted to a steering systemcomprising more than one steered font axle. It could also be adapted toa marine propulsion system comprising more than one marine propulsionunit.

An embodiment of the invention will now be described by way of examplewith reference to the following drawings in which:

FIG. 1 is a perspective view from above and behind, of the front wheelsteering arrangement of an amphibian with retractable wheels accordingto the invention;

FIG. 2 is a side view of one front wheel arrangement of the amphibian ofFIG. 1 in road mode, with the front wheel removed for clarity;

FIG. 3 is a side view of the front wheel arrangement of FIG. 2, in thewheel retracted position in marine mode; and

FIG. 4 is a plan view of a marine propulsion unit of the amphibian ofFIG. 1, as steered by de steering arrangement of FIG. 1.

In the drawings, FIG. 1 shows on the left the front wheel hub assembly 2with brake disc 4 and brake caliper 6. The hub assembly 2 is mounted toupper and lower wishbones 8 and 9, which enable piston and cylinderarrangement 12 to raise the front wheel from the position shown in FIG.2 to that shown in FIG. 3. In doing so, link 14 (there is the samearrangement on the other side, shown at 14′) folds upwards to theposition 14″ shown in broken lines in FIG. 1. (The folded position 14″is shown for link 14′, for clarity). FIG. 3 also shows part of the hull10 to which wishbones 8 and 9 arm mounted via a mounting plate (omittedfor clarity). The hull 10 has a planing bottom 11.

Coupled to links 14 and 14′ is power assisted transversely mountedsteering rack unit 16, actuated by a pinion in housing 18; which in turnis actuated by an inner steering column on axis 20, and finally by asteering wheel 22, shown diagrammatically at a severely reduced scalefor clarity.

The rack movement is some 114 mm lock to lock, whilst the steering wheelhas 2,3 turns from lock to lock. Mounted to rack arm 24 is bracket 26,to which is in turn mounted link rod 28; to the other ed of which ismounted bell crank 30. Crank 30 is pivoted about pivot 32, and coupledto push-pill cable 34; which is slidably mounted in flexible casing orsleeve 36. The coupling between rack arm 24 and bell crack 30 is suchthat rod 28 is in front of steering column 20. This ensures economy ofspace.

At the rear of the vehicle is marine propulsion unit 40, shown in FIG.4, which has a steering nozzle 42 pivotally mounted to propulsionconduit housing 44 at 46. Bolted to said nozzle is steering arm 48, towhich the push-pull cable is coupled. Sleeve 36 is fixedly secured at 50to flange 52 of housing 4. Sleeve 36 is 15 to 17 mm in diameter, whilstcable 34 is 12 to 13 mm in diameter. The cable and sleeve are arrangedin the vehicle with a minimum bending radius of 150 mm. A reversingbucket nay be fitted to the steering nozzle, as is known in the marineengineering art.

It should be noted that further refinements may be made to the steeringsystem described above without departing from the essential inventiveconcept. For example, the system is particularly suited to be adapted toa road steering system using “steer by wire”; that is, not having amechanical linkage between the steering wheel and the transverselymounted steering element. Such a system would be particularlyadvantageous to a amphibian, in that the bulkhead ahead of the driverwould be more easily sealed against passage of water without aconventional steering column passing therethrough. The power assistedsteering system may be hydraulic, hybrid hydraulic/electric, electric,or magnetic. The input to the marine steering system could be taken froma steered rear axle. This would, however, require some means of controlwhich accounted for the fact that most rear wheel steering systemssometimes steer the rear wheels out of phase with the front wheels; andsometimes in phase with them.

Where two or more marine propulsion units are used, their steeringnozzles may be mechanically linked to ensure that they turn in phasewith each other. Such a linkage may have some geometry comparable toAckermann geometry for road steering. Where two or more front steeredaxles are used, they may both have hydraulic cylinders to steer theirrespective wheels. With two steered front axles and two marine drives, acable could be taken from each steered axle to a respective marinedrive.

The fixing of the cable sleeve to the jet flange described above is asimple and cheap solution. It may be preferred to fix the cable sleeveto a jet flange by means of a bracket and locknuts, thereby allowinglongitudinal adjustment of the cable sleeve; as is known in the marineengineering art.

The steering system described offers a fixed ratio between road andmarine steering, which is fixed at the design stage by the lengths ofthe arms on the bell crank. The drawback of such a fixed ratio isconsidered to be outweighed by the system's compactness, simplicity, andlight weight; each of which are particularly helpful where retractablewheels are fitted.

1. An amphibious vehicle having retractable wheels and a planning hull,a marine propulsion unit, front wheels arranged to be steered by meansof a power assisted transversely mounted element, an actuating rodmounted to said element, the rod arranged for transverse movement, and aflexible coupling means connecting said actuating rod to a steerablepart of the marine propulsion unit, so that transverse movement of saidelement steers the part of the marine propulsion unit.
 2. An amphibiousvehicle according to claim 1, the transversely mounted element is linkedby means of a link to each wheel, the links arranged to fold upwards onretracting the wheels.
 3. An amphibious vehicle according to claim 1,wherein both road and marine steering are arranged to be operatedsimultaneously.
 4. An amphibious vehicle according to claim 1, whereinthe transversely mounted element is a rack and pinion steering system.5. An amphibious vehicle according to claim 1, wherein the flexiblecoupling means is a push-pull cable.
 6. An amphibious vehicle accordingto claim 5, wherein the push-pull cable is coupled to the actuating rodthrough a bell crank means.
 7. An amphibious vehicle according to claim6, wherein the actuating rod connects the bell crank means to thetransversely mounted element, and said actduating rod is mounted infront of a steering column.
 8. An amphibious vehicle according to claim1, wherein more than one front steered axle is fitted.
 9. An amphibiousvehicle according to claim 1, wherein more than one steered marinepropulsion unit is fitted.
 10. (canceled)